Stormwater Symposium

Oral

397582 - Accumulation and transport of road de-icers in surface waters

Tuesday, June 5
10:30 AM - 12:00 PM
Location: Greenway AB
Co-Authors: Ben Janke, Minneapolis, MN – University of Minnesota; Heinz Stefan, Minneapolis, MN – University of Minnesota

The accumulation of chloride in surface waters and groundwater from road de-icing is a growing problem in cold regions of the country, and has been the topic of a series of studies at the University of Minnesota St. Anthony Falls Lab (SAFL). The first study, completed in 2008, found that about 75% of all chloride from road salt applied in the Twin Cities metro area is accumulating in surface waters, soils, and groundwater, with the remaining 25% exported from the region by the Mississippi River. A recently completed follow-on study monitored chloride transport in small (<300 acres) catchments in the Twin Cities metro area. A 28 acre curb-and-gutter catchment exported 34 to 63% of applied de-icing chloride in surface runoff, with a delay of about 2 to 4 weeks between application and export. In contrast, a pervious highway ditch exported only 6% of applied chloride in surface runoff. Rain-on-snow events produced some of the largest chloride export events in these watersheds. Detention ponds were found to add substantial chloride retention time to a watershed, with persistent, high concentrations of chloride observed at the pond bottoms. Based on the results of the study, the use of snowmelt capture for chloride mitigation was explored. Current chloride research at SAFL includes studies on the accumulation and release of chloride in soils near roadways, and on the potential benefits of pervious pavement for reducing de-icer usage.

William Herb

Research Associate
University of Minnesota

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